Enhancing Hole Utilization via PHI-NiO x p–n Heterojunctions for C–H Bond Activation

Abstract Efficient photocatalysis C–H bond activation under mild conditions remains a long-standing challenge due to the limited charge separation efficiency and insufficient utilization of photogenerated carriers. Herein, a poly(heptazine imide) (PHI) and NiOx p–n heterojunction (PHI-NiOx) is engineered to induce interfacial charge redistribution and construct a built-in electric field, enabling directional charge transfer and enhanced hole utilization. As a result, the optimized catalyst achieves efficient visible-light-driven oxidation of toluene to benzaldehyde, delivering a production rate of 1245 μmol g–1 h–1, which is 10 times higher than that of pristine PHI. Kinetic isotope effect and radical trapping experiments confirm that C–H bond cleavage is the rate-determining step and proceeds via a hole-dominated oxidation pathway. Mechanistic studies combining in situ spectroscopy and density functional theory calculations demonstrate that the heterojunction facilitates charge separation, accelerates interfacial charge transfer, and lowers the energy barrier of the key dehydrogenation step. This work highlights the critical role of interface engineering in modulating charge dynamics and reaction pathways, providing a versatile strategy for designing high-performance photocatalysts for selective organic transformations under mild conditions.